Non-Hodgkin lymphomas (NHLs) are a heterogeneous group of lymphoproliferative diseases. NHL usually originates in lymphoid tissues and can spread to other organs (National Cancer Institute, 2015).
NHL is the seventh most common type of cancer and represents 4.3% of all new cancer cases in the U.S. (SEER Stat facts, 2014). It is the most common hematological malignancy both in Europe and the U.S. (Inoges et al., 2014).
The probability to develop NHL increases with age: The median age at the time point of diagnosis is 66 years. NHL is more common in people of Caucasian descent (21 cases per 100,000 persons), followed by Africans (15 cases per 100,000 persons) and Asians (14 cases per 100,000 persons). Men have a higher risk to develop NHL than women (23.9 cases per 100,000 males vs. 16.3 cases per 100,000 females) (SEER Stat facts, 2014).
The 5-year relative survival of NHL patients is 70% and varies with the cancer stage at the time point of diagnosis. For localized disease, the 5-year relative survival is 82%. If NHL has spread to different parts of the body, the 5-year relative survival decreases to 73.8% for regional and 62.4% for distant stage disease (SEER Stat facts, 2014). Risk factors include (high) age, male gender, ethnicity (Caucasian), exposure to benzene or radiation, HIV, autoimmune diseases, infections with HTLV-1, EBV or HHV8, infections with Helicobacter pylori, Chlamydophila psittaci, Campylobacter jejuni or HCV, (high) body weight and breast implants (American Cancer Society, 2015).
NHL has over 60 subtypes. The three most common subtypes are diffuse large B-cell lymphoma (DLBCL, the most common subtype), follicular lymphoma (FL, the second most common subtype) and small lymphocytic lymphoma/chronic lymphocytic lymphoma (SLL/CLL, the third most common subtype). DLBCL, FL and SLL/CLL account for about 85% of NHL (Li et al., 2015).
Diffuse large B-cell lymphoma (DLBCL) is the most common NHL type and comprises 30% of all NHLs. DLBCL belongs to the aggressive NHL subtypes and most patients show a quickly progressing disease. The International Prognostic Index (IPI) for aggressive NHL uses five significant risk factors prognostic for overall survival:
1. Age (≤60 years vs. >60 years)
2. Serum lactate dehydrogenase (LDH) (normal vs. elevated)
3. Performance status (0 or 1 vs. 2-4)
4. Stage (stage I or II vs. stage III or IV)
5. Extranodal site involvement (0 or 1 vs. 2-4).
Patients with two or more risk factors have a less than 50% chance of relapse-free survival and overall survival at 5 years. Patients with rearrangements of the bcl-2 and myc gene and/or overexpression of myc have a particularly poor prognosis. DLBCL patients co-expressing CD20 and CD30 have a more favorable prognosis and are predestined for an anti-CD30-specific therapy (National Cancer Institute, 2015).
Follicular lymphoma (FL) is the second most common NHL type and comprises 20% of all NHLs and 70% of all indolent lymphomas. More than 90% of the patients exhibit rearrangement of the bcl-2 gene. Most patients are 50 years or older at the time point of diagnosis and have advanced stage disease. The Follicular Lymphoma International Prognostic Index (FLIPI) uses five significant risk factors prognostic for overall survival:
1. Age (≤60 years vs. >60 years)
2. Serum lactate dehydrogenase (LDH) (normal vs. elevated)
3. Stage (stage I or II vs. stage III or IV)
4. Hemoglobin level (≥120 g/L vs. <120 g/L)
5. Number of nodal areas (≤4 vs. >4).
Patients with none or one risk factor have an 85% 10-year survival rate. Patients with three or more risk factors have a 40% 10-year survival rate (National Cancer Institute, 2015).
Diagnosis of NHL is done on an excisional biopsy of an abnormal lymph node or an incisional biopsy of an involved organ. Besides immunohistochemistry, cytogenetics, molecular genetics and fluorescent in situ hybridization (FISH) are used to clarify the diagnosis (Armitage, 2007).
Staging is done after the evaluation of the patients' history, physical examination and laboratory studies including hematologic parameters, screening chemistry studies and especially a test for serum lactate dehydrogenase (LDH) level. Imaging studies include computed tomograms of the chest, abdomen and pelvis and a PET scan (Armitage, 2007).
Determining for prognosis and treatment decision is the differentiation between indolent NHL types and aggressive NHLs. Indolent NHLs progress slowly, have a good prognosis and respond in early stages to radiation therapy, chemotherapy and immunotherapy, but are not curable in advanced stages. Aggressive NHLs progress quickly, but are responsive to intensive combination chemotherapy (National Cancer Institute, 2015).
Depending on the disease stage at the time point of diagnosis patients are classified into prognostic groups (National Cancer Institute, 2015) as follows:
StagePrognostic groupsIInvolvement of a single lymphatic site (nodal region, Waldeyerring, thymus or spleen (I).Localized involvement of a single extra-lymphatic organ or sitein the absence of any lymph node involvement (IE).IIInvolvement of two or more lymph node regions on the same sideof the diaphragm (II).Localized involvement of a single extra-lymphatic organ or sitein association with regional lymph node involvement with orwithout involvement of other lymph node regions on the sameside of the diaphragm (IIE). The number of regions involved maybe indicated by a subscript Arabic numeral (for example II3).IIIInvolvement of lymph node regions on both sides of the diaphragm(III), which also may be accompanied by extra-lymphatic extensionin association with adjacent lymph node involvement (IIIE) or byinvolvement of the spleen (IIIS) or both (IIIE, IIIS).IVDiffuse or disseminated involvement of one or more extra-lymphatic organs, with or without associated lymph nodeinvolvement.Isolated extra-lymphatic organ involvement in the absence ofadjacent regional lymph node involvement, but in conjunctionwith disease in distant site(s). Stage IV includes any involvementof the liver or bone marrow, lungs (other than by direct extensionfrom another site), or cerebrospinal fluid.
The Ann Arbor staging system is usually used for patients with NHL. In this system, stage I, stage II, stage III and stage IV are sub-classified in to the categories A and B. Patients with well-defined generalized symptoms receive the designation B, while patients without these symptoms belong to category A. Category B symptoms include unexplained loss of more than 10% of body weight in the six months before diagnosis, unexplained fever with temperatures above 38° C. and drenching night sweats. Specialized designations are used depending on the involvement of specific organs/sites (National Cancer Institute, 2015) as follows:
DesignationSpecific sitesEExtranodal lymphoid malignancies near majorlymphatic aggregatesNNodesHLiverLLungMBone marrowSSpleenPPleuraOBoneDSkin
To assign a precise stage, patients receive a clinical stage (CS) based on the findings of the clinical evaluation and a pathologic stage (PS) based on the findings of invasive procedures beyond the initial biopsy (National Cancer Institute, 2015).
Treatment of NHL depends on the histologic type and stage. Standard treatment options include (National Cancer Institute, 2015):
StageStandard treatment optionIndolent,Radiation therapystage I and contiguousRituximab ± chemotherapystage II NHLWatchful waitingOther therapies as designated for patientswith advanced-stage diseaseIndolent,Watchful waiting for asymptomatic patientsnon-contiguousRituximabstage II/III/IV NHLPurine nucleoside analogsAlkylating agents ± steroidsCombination chemotherapyYttrium-90-labeled ibritumomab tiuxetanMaintenance rituximabIndolent,Chemotherapy (single agent or combination)Recurrent NHLRituximabLenalidomideRadiolabeled anti-CD20 monoclonalantibodiesPalliative radiation therapyAggressive,R-CHOP ± (involved-field radiationstage I and contiguoustherapy) IF-XRTstage II NHLAggressive, non-R-CHOPcontiguous stageOther combination chemotherapyII/III/IV NHLLymphoblastic lymphomaIntensive therapyRadiation therapyDiffuse, small,Aggressive multi-drug regimensnoncleaved-cell/BurkittCentral nervous system (CNS) prophylaxislymphomaAggressive,Bone marrow or stem cell transplantationrecurrent NHLRe-treatment with standard agentsPalliative radiation therapy
Indolent, stage I and contiguous stage II NHL: Standard treatment options include radiation therapy, rituximab (anti-CD20 monoclonal antibody)±chemotherapy, watchful waiting and other therapies as designated for patients with advanced-stage disease.
Indolent, non-contiguous stage II/III/IV NHL: Standard treatment options include watchful waiting for asymptomatic patients, rituximab, obinutuzumab (anti-CD20 monoclonal antibody), purine nucleoside analogs (fludarabine, 2-chlorodeoxyadenosine), alkylating agents (cyclophosphamide, chlorambucil)±steroids, bendamustine, combination chemotherapy (CVP, C-MOPP (cyclophosphamide, vincristine, procarbazine, and prednisone), CHOP, FND (fludarabine, mitoxantrone±dexamethasone)), yttrium-labeled ibritumomab tiuxetan and maintenance rituximab. Rituximab (R) is considered first-line therapy, either alone or in combination with other agents (R-Bendamustine, R-F (fludarabine), R-CVP (cyclophosphamide, vincristine, and prednisone), R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone), R-FM (fludarabine, mitoxantrone), R-FCM (fludarabine, cyclophosphamide, and mitoxantrone)). Under clinical evaluation are bone marrow transplantation (BMT) or peripheral stem cell transplantation (PSCT), idiotype vaccines and radiolabeled monoclonal antibodies (ofatumumab: anti-CD20 monoclonal antibody).
Indolent, recurrent NHL: Standard treatment options include chemotherapy (single agent or combination), rituximab, lenalidomide, radiolabeled anti-CD20 monoclonal antibodies (yttrium-90 ibritumomab) and palliative radiation therapy. Treatment options under clinical evaluation include SCTs.
Aggressive, stage I and contiguous stage II NHL: Standard treatment options include R-CHOP±IF-XRT. Treatment options under clinical evaluation include R-ACVBP (rituximab+doxorubicin, cyclophosphamide, vindesine, bleomycin, prednisone).
Aggressive, non-contiguous stage II/III/IV NHL: Standard treatment options include combination chemotherapy±local-field radiation therapy. Drug combinations include ACVBP, CHOP, CNOP (cyclophosphamide, mitoxantrone, vincristine, prednisone), m-BACOD (methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, dexamethasone, leucovorin), MACOP-B (methotrexate, doxorubicin, cyclophosphamide, vincristine, prednisone fixed dose, bleomycin, leucovorin), ProMACE CytaBOM (prednisone, doxorubicin, cyclophosphamide, etoposide, cytarabine, bleomycin, vincristine, methotrexate, leucovorin), R-CHOP. Under clinical evaluation are BMT and SCT.
Lymphoblastic lymphoma: Standard treatment options include intensive therapy and radiation therapy.
Diffuse, small noncleaved-cell/Burkitt lymphoma: Standard treatment options include aggressive multidrug regimens and CNS prophylaxis.
Aggressive, recurrent NHL: Standard treatment options include BMT or SCT, re-treatment with standard agents (rituximab, radiolabeled anti-CD20 monoclonal antibodies, denileukin diftitox (a fusion protein combining diphtheria toxin and interleukin-2)) and palliative radiation therapy. Treatment options under clinical evaluation include SCT (National Cancer Institute, 2015).
Spontaneous tumor regression can be observed in lymphoma patients. Therefore, active immunotherapy is a therapy option (Palomba, 2012). An important vaccination option includes Id vaccines. B lymphocytes express surface immunoglobulins with a specific amino acid sequence in the variable regions of their heavy and light chains, unique to each cell clone (=idiotype, Id). The idiotype functions as a tumor associated antigen.
Passive immunization includes the injection of recombinant murine anti-Id monoclonal antibodies alone or in combination with IFN alpha, IL2 or chlorambucil.
Active immunization includes the injection of recombinant protein (Id) conjugated to an adjuvant (KLH), given together with GM-CSF as an immune adjuvant. Tumor-specific Id is produced by hybridoma cultures or using recombinant DNA technology (plasmids) by bacterial, insect or mammalian cell culture.
Three phase III clinical trials have been conducted (Biovest, Genitope, Favrille). In two trials patients had received rituximab. GM-CSF was administered in all three trials. Biovest used hybridoma-produced protein, Genitope and Favrille used recombinant protein. In all three trials Id was conjugated to KLH. Only Biovest had a significant result.
Vaccines other than Id include the cancer-testis antigens MAGE, NY-ESO1 and PASD-1, the B-cell antigen CD20 or cellular vaccines. The vaccines consist of DCs pulsed with apoptotic tumor cells, tumor cell lysate, DC-tumor cell fusion or DCs pulsed with tumor-derived RNA. In situ vaccination involves the vaccination with intra-tumoral CpG in combination with chemotherapy or irradiated tumor cells grown in the presence of GM-CSF and collection/expansion/re-infusion of T cells.
Vaccinations with antibodies that alter immunologic checkpoints are comprised of anti-CD40, anti-OX40, anti-41BB, anti-CD27, anti-GITR (agonist antibodies that directly enhance anti-tumor response) or anti-PD1, anti-CTLA-4 (blocking antibodies that inhibit the checkpoint that would hinder the immune response). Examples are ipilimumab (anti-CTLA-4) and CT-011 (anti-PD1) (Palomba, 2012).
Considering the severe side-effects and expense associated with treating cancer, there is a need to identify factors that can be used in the treatment of cancer in general and NHL in particular. There is also a need to identify factors representing biomarkers for cancer in general and NHL in particular, leading to better diagnosis of cancer, assessment of prognosis, and prediction of treatment success.
Immunotherapy of cancer represents an option of specific targeting of cancer cells while minimizing side effects. Cancer immunotherapy makes use of the existence of tumor associated antigens.
The current classification of tumor associated antigens (TAAs) comprises the following major groups:
a) Cancer-testis antigens: The first TAAs ever identified that can be recognized by T cells belong to this class, which was originally called cancer-testis (CT) antigens because of the expression of its members in histologically different human tumors and, among normal tissues, only in spermatocytes/spermatogonia of testis and, occasionally, in placenta. Since the cells of testis do not express class I and II HLA molecules, these antigens cannot be recognized by T cells in normal tissues and can therefore be considered as immunologically tumor-specific. Well-known examples for CT antigens are the MAGE family members and NY-ESO-1.
b) Differentiation antigens: These TAAs are shared between tumors and the normal tissue from which the tumor arose. Most of the known differentiation antigens are found in melanomas and normal melanocytes. Many of these melanocyte lineage-related proteins are involved in biosynthesis of melanin and are therefore not tumor specific but nevertheless are widely used for cancer immunotherapy. Examples include, but are not limited to, tyrosinase and Melan-A/MART-1 for melanoma or PSA for prostate cancer.
c) Over-expressed TAAs: Genes encoding widely expressed TAAs have been detected in histologically different types of tumors as well as in many normal tissues, generally with lower expression levels. It is possible that many of the epitopes processed and potentially presented by normal tissues are below the threshold level for T-cell recognition, while their over-expression in tumor cells can trigger an anticancer response by breaking previously established tolerance. Prominent examples for this class of TAAs are Her-2/neu, survivin, telomerase, or WT1.
d) Tumor-specific antigens: These unique TAAs arise from mutations of normal genes (such as β-catenin, CDK4, etc.). Some of these molecular changes are associated with neoplastic transformation and/or progression. Tumor-specific antigens are generally able to induce strong immune responses without bearing the risk for autoimmune reactions against normal tissues. On the other hand, these TAAs are in most cases only relevant to the exact tumor on which they were identified and are usually not shared between many individual tumors. Tumor-specificity (or -association) of a peptide may also arise if the peptide originates from a tumor- (-associated) exon in case of proteins with tumor-specific (-associated) isoforms.
e) TAAs arising from abnormal post-translational modifications: Such TAAs may arise from proteins which are neither specific nor overexpressed in tumors but nevertheless become tumor associated by posttranslational processes primarily active in tumors. Examples for this class arise from altered glycosylation patterns leading to novel epitopes in tumors as for MUC1 or events like protein splicing during degradation which may or may not be tumor specific.
f) Oncoviral proteins: These TAAs are viral proteins that may play a critical role in the oncogenic process and, because they are foreign (not of human origin), they can evoke a T-cell response. Examples of such proteins are the human papilloma type 16 virus proteins, E6 and E7, which are expressed in cervical carcinoma.
T-cell based immunotherapy targets peptide epitopes derived from tumor-associated or tumor-specific proteins, which are presented by molecules of the major histocompatibility complex (MHC). The antigens that are recognized by the tumor specific T lymphocytes, that is, the epitopes thereof, can be molecules derived from all protein classes, such as enzymes, receptors, transcription factors, etc. which are expressed and, as compared to unaltered cells of the same origin, usually up-regulated in cells of the respective tumor.
There are two classes of MHC-molecules, MHC class I and MHC class II. MHC class I molecules are composed of an alpha heavy chain and beta-2-microglobulin, MHC class II molecules of an alpha and a beta chain. Their three-dimensional conformation results in a binding groove, which is used for non-covalent interaction with peptides.
MHC class I molecules can be found on most nucleated cells. They present peptides that result from proteolytic cleavage of predominantly endogenous proteins, defective ribosomal products (DRIPs) and larger peptides. However, peptides derived from endosomal compartments or exogenous sources are also frequently found on MHC class I molecules. This non-classical way of class I presentation is referred to as cross-presentation in the literature (Brossart and Bevan, 1997; Rock et al., 1990). MHC class II molecules can be found predominantly on professional antigen presenting cells (APCs), and primarily present peptides of exogenous or transmembrane proteins that are taken up by APCs e.g. during endocytosis, and are subsequently processed. Complexes of peptide and MHC class I are recognized by CD8-positive T cells bearing the appropriate T-cell receptor (TCR), whereas complexes of peptide and MHC class II molecules are recognized by CD4-positive-helper-T cells bearing the appropriate TCR. It is well known that the TCR, the peptide and the MHC are thereby present in a stoichiometric amount of 1:1:1.
CD4-positive helper T cells play an important role in inducing and sustaining effective responses by CD8-positive cytotoxic T cells. The identification of CD4-positive T-cell epitopes derived from tumor associated antigens (TAA) is of great importance for the development of pharmaceutical products for triggering anti-tumor immune responses (Gnjatic et al., 2003). At the tumor site, T helper cells, support a cytotoxic T cell- (CTL-) friendly cytokine milieu (Mortara et al., 2006) and attract effector cells, e.g. CTLs, natural killer (NK) cells, macrophages, and granulocytes (Hwang et al., 2007).
In the absence of inflammation, expression of MHC class II molecules is mainly restricted to cells of the immune system, especially professional antigen-presenting cells (APC), e.g., monocytes, monocyte-derived cells, macrophages, dendritic cells. In cancer patients, cells of the tumor have been found to express MHC class II molecules (Dengjel et al., 2006).
Elongated (longer) peptides of the invention can act as MHC class II active epitopes. T-helper cells, activated by MHC class II epitopes, play an important role in orchestrating the effector function of CTLs in anti-tumor immunity. T-helper cell epitopes that trigger a T-helper cell response of the TH1 type support effector functions of CD8-positive killer T cells, which include cytotoxic functions directed against tumor cells displaying tumor-associated peptide/MHC complexes on their cell surfaces. In this way tumor-associated T-helper cell peptide epitopes, alone or in combination with other tumor-associated peptides, can serve as active pharmaceutical ingredients of vaccine compositions that stimulate anti-tumor immune responses.
It was shown in mammalian animal models, e.g., mice, that even in the absence of CD8-positive T lymphocytes, CD4-positive T cells are sufficient for inhibiting manifestation of tumors via inhibition of angiogenesis by secretion of interferon-gamma (IFNγ) (Beatty and Paterson, 2001; Mumberg et al., 1999). There is evidence for CD4 T cells as direct anti-tumor effectors (Braumuller et al., 2013; Tran et al., 2014).
Since the constitutive expression of HLA class II molecules is usually limited to immune cells, the possibility of isolating class II peptides directly from primary tumors was previously not considered possible. However, Dengjel et al. were successful in identifying a number of MHC Class II epitopes directly from tumors (WO 2007/028574, EP 1 760 088 B1).
Since both types of response, CD8 and CD4 dependent, contribute jointly and synergistically to the anti-tumor effect, the identification and characterization of tumor-associated antigens recognized by either CD8+ T cells (ligand: MHC class I molecule+peptide epitope) or by CD4-positive T-helper cells (ligand: MHC class II molecule+peptide epitope) is important in the development of tumor vaccines.
For an MHC class I peptide to trigger (elicit) a cellular immune response, it also must bind to an MHC-molecule. This process is dependent on the allele of the MHC-molecule and specific polymorphisms of the amino acid sequence of the peptide. MHC-class-I-binding peptides are usually 8-12 amino acid residues in length and usually contain two conserved residues (“anchors”) in their sequence that interact with the corresponding binding groove of the MHC-molecule. In this way, each MHC allele has a “binding motif” determining which peptides can bind specifically to the binding groove.
In the MHC class I dependent immune reaction, peptides not only have to be able to bind to certain MHC class I molecules expressed by tumor cells, they subsequently also have to be recognized by T cells bearing specific T cell receptors (TCR).
For proteins to be recognized by T-lymphocytes as tumor-specific or -associated antigens, and to be used in a therapy, particular prerequisites must be fulfilled. The antigen should be expressed mainly by tumor cells and not, or in comparably small amounts, by normal healthy tissues. In a preferred embodiment, the peptide should be over-presented by tumor cells as compared to normal healthy tissues. It is furthermore desirable that the respective antigen is not only present in a type of tumor, but also in high concentrations (i.e. copy numbers of the respective peptide per cell). Tumor-specific and tumor-associated antigens are often derived from proteins directly involved in transformation of a normal cell to a tumor cell due to their function, e.g. in cell cycle control or suppression of apoptosis. Additionally, downstream targets of the proteins directly causative for a transformation may be up-regulated und thus may be indirectly tumor-associated. Such indirect tumor-associated antigens may also be targets of a vaccination approach (Singh-Jasuja et al., 2004). It is essential that epitopes are present in the amino acid sequence of the antigen, in order to ensure that such a peptide (“immunogenic peptide”), being derived from a tumor associated antigen, leads to an in vitro or in vivo T-cell-response.
Basically, any peptide able to bind an MHC molecule may function as a T-cell epitope. A prerequisite for the induction of an in vitro or in vivo T-cell-response is the presence of a T cell having a corresponding TCR and the absence of immunological tolerance for this particular epitope.
Therefore, TAAs are a starting point for the development of a T cell based therapy including but not limited to tumor vaccines. The methods for identifying and characterizing the TAAs are usually based on the use of T-cells that can be isolated from patients or healthy subjects, or they are based on the generation of differential transcription profiles or differential peptide expression patterns between tumors and normal tissues. However, the identification of genes over-expressed in tumor tissues or human tumor cell lines, or selectively expressed in such tissues or cell lines, does not provide precise information as to the use of the antigens being transcribed from these genes in an immune therapy. This is because only an individual subpopulation of epitopes of these antigens are suitable for such an application, since a T cell with a corresponding TCR has to be present and the immunological tolerance for this particular epitope needs to be absent or minimal. In a very preferred embodiment of the invention it is therefore important to select only those over- or selectively presented peptides against which a functional and/or a proliferating T cell can be found. Such a functional T cell is defined as a T cell, which upon stimulation with a specific antigen can be clonally expanded and is able to execute effector functions (“effector T cell”).
In case of targeting peptide-MHC by specific TCRs (e.g. soluble TCRs) and antibodies or other binding molecules (scaffolds) according to the invention, the immunogenicity of the underlying peptides is secondary. In these cases, the presentation is the determining factor.